The term “traffic flow data” as used in this specification means all types of sensor and measurement data from and relating to vehicles of moving and stationary traffic that can be collected on the level of granularity of individual vehicles and can provide an overview of the traffic situation, the “traffic flow” in a road network or a section thereof in the form of, e.g., a statistical analysis over several vehicles.
Modern vehicles have a variety of sensors for the generation of measurement data, such as speed, acceleration and deceleration, data from the Antilock Braking System (ABS) and Electronic Stability Program (ESP) systems of the vehicle, status of the lighting and heating systems, environmental and weather data such as daylight, outside temperature, air humidity, visibility (fog), data from camera and radar systems of the vehicle for detecting the surrounding traffic and hazards, etc. The multitude of measurement data from the vehicle is further increased by measurement data of electronic accessory devices (“on-board units”, OBUs), e.g. satellite navigation receivers and/or transceivers for radio communication with roadside radio beacons (“Roadside Units”, RSUs). The term “radio beacon” as used herein refers to devices generally used to transmit and receive wireless radio signals, including wireless radio beacon signals. On-board units can receive measurement data of the vehicle as well as, by means of its own sensors, acquire measurement data relating to the vehicle and/or its environment, e.g., positions and speeds measured by means of satellite navigation from radio communications with radio beacons or mobile networks, environmental data from its own weather sensors, etc.
However, determining meaningful traffic flow data is a non-trivial problem in practice even with vehicles equipped as such. A transmission of the measurement data of all vehicles to a central analysis unit is not realistic due to the large volume of data and the limited transmission capacities of currently available wireless channels, e.g., of mobile radio systems. Moreover, the measurement data generated by the individual vehicles are highly redundant in dense traffic and of little use with “fair weather conditions” (low traffic, good weather, no incidents or accidents). Therefore, present systems for collecting traffic flow data only use a limited number of specially equipped vehicles, e.g. taxis, which go with the flow of the traffic to provide a representative picture of the traffic situation or the environmental situation. However, this firstly requires a special fleet of vehicles, and secondly requires a permanent data link from these vehicles to the analysis center, normally a data link to a wireless network, which is expensive and requires many resources.
The technical report ETSI TR 102 898 “Machine to Machine Communications (M2M); Use cases of Automotive Applications in M2M capable networks”, V 0.4.0, September 2010, Chapter 5.2.3, describes scenarios for traffic information services which distribute information from a central unit via wireless networks to OBUs, which in turn send traffic flow data to the central unit in the case of specific events. This design can be attributed to the aforementioned non-specific data collection solutions having the disadvantage of an uncontrollable high amount of data without any possibility of a location-specific access to the data-generating vehicles in the collection process.